Part marking systems address the need to trace components including aircraft, surgical, automotive parts, or other like parts for the duration of their lifetime. These markings can allow parts to be identified and traced to their origin. Additionally these markings can facilitate the assembly of complex structures by providing reference markings or instructions at the assembly point for use in assembling and aligning various parts. To assist in assembly, automated ink jet marking systems often mark locations of hardware and fasteners on part surfaces. This allows the operators to quickly and accurately locate and align sub-assemblies to larger assemblies. Additionally, this avoids the need to construct complicated and expensive jigs to locate sub-assemblies and fasteners.
Current inkjet marking systems provide only horizontal or vertical firing. This adequately addresses the marking of horizontal and vertical surfaces. However, this fails to address the need to appropriately mark components with geometrically confined spaces or surfaces at non-normal angles to the ink jet marking system. Currently, known parts marking systems lack the ability to handle irregular shaped and cylindrical parts having various surface projections such as flanges or stiffeners that are located at non-normal angles to the parts surface. Previously these complex structures were marked by hand or required expensive and unique tooling in order to properly mark attachment locations for the machining of the part.
Additionally, because current inkjet effecters fire only in the horizontal or in the vertical direction, alignment errors may be induced on non-planar surfaces by the angle between the ink stream and the surface normal of the part to be marked. Another problem arises from constraints associated with part geometry depending on the depth and the size of the area to be marked as existing marking heads cannot reach into confined spaces.
FIG. 1 illustrates the problems associated with marking parts or components 10 wherein the surface normal 12 is at a non-zero angle to the ink stream 14 supplied by the marking head. This results in a displacement of the marking from an intended surface 16 to the actual surface 18. Significant alignment errors can be experienced due to an accumulated effect of incorrectly synchronizing system alignments as indicated in the graph provided in FIG. 2. These additive errors include: (1) the alignment of the calibration monument; (2) end effector (tool centerpoint (TCP)); (3) vision or parts location system (vision system centerpoint); (4) part alignment and orientation in space; and (5) work envelope of the robot. Therefore a need exists for a parts marking system capable of accurately marking parts having surfaces located at a non-normal angles to the end-effector or within confined spaces.